To obtain a pn junction type light-emitting diode (LED) which operates stably for a long period of time, it is important to provide technical means capable of preventing a reverse overcurrent from accidentally passing to a pn junction type light-emitting section due to, for example, static electricity. Conventionally, a method of electrically protecting the LED by connecting an electronic part such as a Zener diode to the LED has often been used for the purpose of improving an electric breakdown property of the LED. Especially for a gallium nitride (GaN) base or aluminum phosphide gallium indium (AlGaInP) base LEDs provided with a pn junction type light-emitting section composed of a thin compound semiconductor layer, means for purposely adding and incorporating a Zener diode to/in an LED drive electric circuit and improving a breakdown voltage property is disclosed (see JP-A 2005-20038 (Patent Document 1)).
Furthermore, JP-A 2005-57228 (Patent Document 2) and JP-A 2000-188425 (Patent Document 3) disclose a technique of improving a breakdown voltage property of an LED by providing an LED drive power circuit in which capacitors and resistors are incorporated in a complicated way.
Furthermore, a technique of improving a breakdown voltage property against an LED reverse voltage by providing a pn junction type LED and a pn junction type protective diode independently of the LED and electrically connecting them in parallel (see JP-A SHO 52-61982 (Patent Document 4)). Furthermore, in addition to the above described technique of providing a pn junction type protective diode as a single element independent of the LED, technical means for avoiding a reverse overvoltage from applying to a pn junction type light-emitting section by providing a pn junction type protective diode on the same substrate adjacently and separately is also disclosed (see JP-A HEI 10-200159 (Patent Document 5)).
However, of the above described prior arts, Patent Documents 1 to 3 require a space for adding an electronic part to the power circuit to improve the breakdown voltage property of the Zener diode and capacitor or the like, which results in a problem that the size of the LED is increased uselessly. Furthermore, increasing the number of electronic parts incorporated in the power circuit to further improve the breakdown voltage property results in a problem of further complicating the circuit assembly technique and making it unavoidable to increase LED manufacturing cost.
Furthermore, as shown in Patent Documents 4 and 5, when a protective diode is used as a single part separately and at the same time electrically connected in parallel to improve the breakdown voltage property against a reverse current which passes to the pn junction type light-emitting section accidentally, a space for arranging the protective diode is required and the chip size of the LED bonded naturally increases. Furthermore, in order to display the function of electrically protecting the pn junction type light-emitting section from an accidental reverse overcurrent, the protective diode provided separately from the LED needs to be provided with an electrode for operating the protective diode itself is necessary in addition to the electrode necessary to pass an operating current to the light-emitting section of the LED. For example, a total of three (see FIG. 4 in Patent Document 4) or a total of four (see FIG. 1 in Patent Document 4) input and output electrodes need to be formed at most for the LED with the pn junction type protective diode as a single unit described in above Patent Document 4, which undoubtedly complicates the process of manufacturing the LED.
On the other hand, means for obtaining an LED having an excellent breakdown voltage property may also be considered which includes a pn junction structure having an operation of protecting, for example, the light-emitting section of the LED from an overcurrent accidentally applied in a reverse direction. This technical means can simply provide an LED having a high breakdown voltage property without purposely adding electronic parts for improving the breakdown voltage property, for example, a protective diode outside the element such as the LED. However, when a semiconductor material having a relatively narrow forbidden width such as silicon single crystal (silicon) as a substrate to form the pn junction structure, the breakdown voltage property of the LED may be improved, but it takes ingenuity to design the structure of the LED as well as the configuration of electrodes for the LED in order to avoid absorption of emitted light by the silicon substrate or the like and obtain an LED with excellent light-emitting intensity.
The present invention has been proposed in view of the above described problems and it is an object of the present invention to provide a light-emitting diode and light-emitting diode lamp capable of reducing the size and cost even when a breakdown voltage is improved and also eliminating the necessity for any protective diode and having excellent light-emitting intensity.